There are many applications in which a bead lock is formed at the end of a malleable cylindrical tube. Such bead locks are utilized to secure the tube to hoses or to some type of fluid device such as a hydraulic pump or valve. Such bead locked tubes are also used for securing tubes to systems carrying fluids such as fuel or brake fluids.
To form the bead lock on the end of a tube, it has been known to utilize a die assembly to radially deform and thereby expand the tube to form the bead lock separate from or external to the fluid connector. These die assemblies typically comprise a holder secured to the tube to prevent undesired axial movement of the tube relative to the die when the forming operation is performed. According to the prior art, the tubing holder and the forming die are moved together thereby radially expanding the tube into the forming surfaces formed on both the holder and the die separate from any type of fluid connector. The fluid connector is then joined to the longer tube by furnace brazing. In that process, the forming surface of the die would deform the surface of the bead lock axially closest to the free end of the tube while the forming surface on the tube holder would form the opposite axial end of the bead lock if one is needed. The heat applied during the brazing process causes the tube to deform slightly resulting in a misaligned assembly that must be either re-worked or discarded.
The disclosure of U.S. Pat. No. 6,572,358 to Blethen describes a die assembly for forming a bead lock on a cylindrical tube which includes a holder which secures the tube against axial movement so that a portion of the tube protrudes outwardly from the holder along a pre-determined axis and in which the holder has a forming surface which lies against the tube to be formed. The die assembly of the '358 patent further includes a first die part having a cylindrical mandrel aligned with and engaging with the tube. In its first position, the holder abuts against the second die part while the second die part is in its extended position. Conversely, as the holder is moved to its second position relative to the first die position the holder moves the second die part to its retracted position thus radially outwardly deforming the bead lock between the forming surface in the holder and the conical surface on the sleeve. Since the through bore formed in the second die part circumscribes and constrains the tube around the bead lock during the entire formation of the bead lock, and also since the holder remains in contact with the second die part during the entire deformation process, the bead lock is not only accurately formed on the tube, but the possibility of a burr forming between the holder and the second die part is altogether eliminated.
Thus, it is evident that while this prior art die assembly for forming a bead lock on a cylindrical tube produces a satisfactory product, it does so while using a very complicated and expensive piece of forming equipment separate from the fluid connector. More importantly, the bead locked tube is then brazed to a longer length of tubing and all of the assembled pieces must be thoroughly cleaned prior to the brazing process. The heat applied for brazing warps the components in an unpredictable manner requiring re-work or the parts to be discarded.
Another well known method of forming a bead lock on a cylindrical tube is disclosed in U.S. Pat. No. 3,575,033 to Meyer. In the '033 patent, a die member contains an annular passage that surrounds the exterior of a tube end and a guide pin that extends into the passage in the tube beyond the location of a desired bead lock. The tube is clamped into a holder at the approximate location of the bead lock and a force is applied to the die member to move the member toward the holder. This movement deforms the tube wall outward between the die member and the holder, thus forming a bead lock on the tube at a point remote from the tube end and separate from any type of fluid connector. This tubing bead locker does not control the outside diameter of the bead lock formed on the cylindrical tubing so that the process itself must be altered and changed to control the outside diameter of the bead lock by varying the degree that the die member is axially moved depending on the wall thickness and spring characteristics of the tube itself. Subsequently, the bead locked tube is assembled to a fluid connector and then brazed to a long tube.
The prior art processes includes cutting the unplated tubes to length; clean the components to prepare for brazing; form the outside diameter of the global nipple; furnace braze the joint; apply a trivalent plating to the joint; inspect for internal rust or corrosion and if required, sand blast and lube; end form the mating end per customer requirement; bend the assembly to print; and finally ship to stock.